Control element of an organic electro-luminescent display and manufacturing process thereof

ABSTRACT

A control element of an organic electro-luminescent display includes a first transistor, a second transistor and a capacitor. The first gate electrode of the first transistor is electrically connected to a scan line, and the first source/drain electrode of the first transistor is electrically connected to a data line. The second gate electrode of the second transistor is electrically connected to the second source/drain electrode of the first transistor. The third source/drain electrode of the second transistor is electrically connected to a working voltage, and the fourth source/drain electrode of the second transistor is electrically connected to a light emitting diode. One end of the capacitor is electrically connected to the second gate electrode. The material of the dielectric layer of the capacitor is different from the material of the gate dielectric of one of the first transistor and the second transistor.

RELATED APPLICATIONS

The present application is based on, and claims priority from, TaiwanApplication Serial Number 94135570, filed Oct. 12, 2005, the disclosureof which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Field of Invention

The present invention relates to a method for manufacturing an organicelectro-luminescent display. More particularly, the present inventionrelates to a method for manufacturing a control element of an organicelectro-luminescent display.

2. Description of Related Art

Organic electro-luminescent displays have the advantages of low cost,long life, low driving voltage, high reaction speed, effective lighting,excellent temperature difference endurance, excellent vibrationendurance, wide viewing angle and dimensional thinness. Manymanufactures have spent great effort and resources researching anddeveloping organic electro-luminescent displays. Thus, organicelectro-luminescent displays may replace thin film transistor liquidcrystal displays in the coming years.

Reference is made to FIGS. 1A˜1E, which are cross-sectional viewsshowing a traditional method for manufacturing a control element of anorganic electro-luminescent display. In FIG. 1A, a first gate electrode122 of a first transistor, a bottom electrode 124 of a capacitor and asecond gate electrode 126 of a second transistor are formed on aninsulating substrate 110.

In FIG. 1B, a dielectric layer 130 is formed over the first gateelectrode 122, the bottom electrode 124 of the capacitor and the secondgate electrode 126 as a gate dielectric of the first transistor and thesecond transistor and a dielectric layer of the capacitor. Then, a firstchannel 142 of the first transistor and a second channel 146 of thesecond transistor are formed over parts of the first gate electrode 122and the second gate electrode 126.

In FIG. 1C, an etching stop layer 150 is formed. The etching stop layer150 is positioned over part of the first gate electrode 122 and thesecond gate electrode 126 for preventing influence from subsequentprocesses.

In FIG. 1D, a doped semiconductor layer 160 is formed over theinsulating substrate 110. Then, the doped semiconductor layer 160 andthe dielectric layer 130 are patterned and a hole 180 is formed toexpose portion of the second gate electrode 126. The source/drainjunctions of the first transistor and the second transistor are formedin this step.

In FIG. 1E, a conductor layer 170 is formed over the insulatingsubstrate 110 and in the hole 180. Then, the conductor layer 170 ispatterned for forming the source/drain electrode of the firsttransistor, the second transistor and a conducting wire. The conductingwire electrically connects the drain of the first transistor, the upperelectrode of the capacitor, and the second gate electrode 126.

The etching stop layer and the hole are formed separately in thetraditional method for manufacturing a control element of an organicelectro-luminescent display. This may increase the amount of stepscomprised by the traditional method such that the cost of the organicelectro-luminescent display is increased and the yield of the organicelectro-luminescent display is decreased.

Moreover, the dielectric layer of the capacitor and the gate dielectricof the first transistor and the second transistor are formed in the samestep in the traditional method for manufacturing a control element of anorganic electro-luminescent display. Thus, the electrical and geometriccharacteristics of the first transistor and the second transistor changeif the capacitance of the capacitor is changed, such that the design ofthe control element of the organic electro-luminescent display islimited.

For the foregoing reasons, there is a need for a manufacturing method ofa control element of an organic electro-luminescent display, whichenables reducing the steps of the method and relaxes the designlimitation.

SUMMARY

It is therefore an aspect of the present invention to provide a methodfor manufacturing a control element of an organic electro-luminescentdisplay, which enables reducing the steps of the method such that thecost of the organic electro-luminescent display is decreased and theyield of the organic electro-luminescent display is enhanced.

It is another aspect of the present invention to provide a method formanufacturing a control element of an organic electro-luminescentdisplay, which can prevent the electrical characteristics of thetransistors of the organic electro-luminescent display from beingchanged when the capacitance of the capacitor of the organicelectro-luminescent display is changed.

It is another aspect of the present invention to provide a method formanufacturing a control element of an organic electro-luminescentdisplay, which can prevent the geometric characteristics of thetransistors of the organic electro-luminescent display from beingchanged when the capacitance of the capacitor of the organicelectro-luminescent display is changed.

In accordance with the foregoing and other aspects of the presentinvention, a control element of an organic electro-luminescent displayincluding a first transistor, a second transistor and a capacitor isprovided. The first gate electrode of the first transistor iselectrically connected to a scan line and the first source/drainelectrode of the first transistor is electrically connected to a dataline. The second gate electrode of the second transistor is electricallyconnected to the second source/drain electrode of the first transistor.The third source/drain electrode of the second transistor iselectrically connected to a working voltage, and the fourth source/drainelectrode of the second transistor is electrically connected to a lightemitting diode. One end of the capacitor is electrically connected tothe second gate electrode, and the other end of the capacitor iselectrically connected to a reference voltage. The material or thicknessof the dielectric layer of the capacitor is different from the materialor thickness of the gate dielectric of one of the first transistor andthe second transistor.

According to one preferred embodiment of the invention, the capacitormay further include a capacitor stack. The capacitor stack is positionedbetween the bottom electrode and the dielectric layer of the capacitor.Moreover, the capacitor stack may include a stack dielectric positionedover the bottom electrode of the capacitor. The material or thickness ofthe stack dielectric is the same as the material or thickness of thegate dielectric of the first transistor and the second transistor.

In accordance with the aspects of the present invention, a method formanufacturing a control element of an organic electro-luminescentdisplay is provided. The method includes the following steps. First, afirst gate electrode, a bottom electrode of a capacitor and a secondgate electrode are formed on an insulating substrate. Then, a first gatedielectric and a first channel are formed over at least part of thefirst gate electrode, and a second gate dielectric and a second channelare formed over at least part of the second gate electrode. Afterward,an etching stop layer is formed over the insulating substrate. Afterforming the etching stop layer, the etching stop layer is patterned toexpose parts of the upper surface of the first channel and the secondchannel for forming source/drain contacts on each of the first channeland the second channel and form a hole on part of the second gateelectrode. Then, a doped semiconductor layer and a conductor layer areformed over the insulating substrate in order. Finally, the conductorlayer and the doped semiconductor layer are patterned for forming afirst source/drain electrode and a second source/drain electrode on thefirst channel, a third source/drain electrode and a fourth source/drainelectrode on the second channel, a conducting wire to electricallyconnect the second source/drain electrode and the second gate electrodevia the hole, and an upper electrode of the capacitor.

According to one preferred embodiment of the invention, a capacitorstack may be formed over the bottom electrode of the capacitor beforeforming the etching stop layer. The capacitor stack may include a stackdielectric positioned over the bottom electrode of the capacitor. Thematerial or thickness of the stack dielectric is the same as thematerial or thickness of the gate dielectric of the first transistor andthe second transistor.

Therefore, the etching stop layer and the hole are formed in the samestep in the foregoing preferred embodiment of the invention, whichreduces the use of photolithography. Photolithography is an expensiveand time-consuming process and can be misaligned. Therefore, reducingthe use of photolithography can reduce the probability of misalignment,cost and time. Moreover, the yield of the organic electro-luminescentdisplay is enhanced by reducing the use of photolithography. Inaddition, the dielectric of the capacitor may be different from the gatedielectric of the first transistor and the second transistor. Thus, theelectrical and geometric characteristics might not need to be changedwhen the capacitance of the capacitor is changed.

It is to be understood that both the foregoing general description andthe following detailed description are by examples and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings where:

FIGS. 1A˜1E are cross-sectional views showing a traditional method formanufacturing a control element of an organic electro-luminescentdisplay;

FIGS. 2A˜2D are cross-sectional views showing a method for manufacturinga control element of an organic electro-luminescent display according toone preferred embodiment of the invention;

FIGS. 3A˜3D are cross-sectional views showing a method for manufacturinga control element of an organic electro-luminescent display according toanother preferred embodiment of the invention; and

FIGS. 4A˜4D are cross-sectional views showing a method for tomanufacturing a control element of an organic electro-luminescentdisplay according to still another preferred embodiment of theinvention;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or likeparts.

Embodiment I

Reference is made to FIGS. 2A˜2D, which are cross-sectional viewsshowing a method for manufacturing a control element of an organicelectro-luminescent display according to one preferred embodiment of theinvention.

In FIG. 2A, a first gate electrode 222, a bottom electrode 224 of acapacitor and a second gate electrode 226 are formed on an insulatingsubstrate 210. The material of the first gate electrode 222, the bottomelectrode 224 of the capacitor and the second gate electrode 226 may bemolybdenum, chromium, iridium, aluminum, titanium, combination thereofor alloy thereof. The forming method may be physical vapor depositionfirst, which deposits a conductor layer, such as sputtering and thenpatterning the conductor layer by, for example, photolithography.

In FIG. 2B, a first gate dielectric 232 and a first channel 242 areformed over at least part of the first gate electrode 222, and a secondgate dielectric 236 and a second channel 246 are formed over at leastpart of the second gate electrode 226. The material of the first gatedielectric 232 and the second gate dielectric 236 may be silicon oxide,silicon nitride or combination thereof. The material of the firstchannel 242 and the second channel 246 may be amorphous silicon. Theforming method may be depositing a dielectric layer and a semiconductorlayer first and then patterning the dielectric layer and thesemiconductor layer, such as by photolithography.

In FIG. 2C, an etching stop layer 250 is formed over the insulatingsubstrate 210. After forming the etching stop layer 250, the etchingstop layer 250 is patterned to expose parts of the upper surface of thefirst channel 242 and the second channel 246 for forming source/draincontacts on each of the first channel 242 and the second channel 246 andform a hole 280 on part of the second gate electrode 226. The materialof the etching stop layer 250 may be silicon oxide, silicon nitride orsilicon oxynitride.

In FIG. 2D, a doped semiconductor layer 260 and a conductor layer 270are formed over the insulating substrate 210 in order. Then, theconductor layer 270 and the doped semiconductor layer 260 are patternedfor forming a first source/drain electrode and a second source/drainelectrode on the first channel 242, a third source/drain electrode and afourth source/drain electrode on the second channel 246, a conductingwire to electrically connect the second source/drain electrode and thesecond gate electrode 226 via the hole 280, and an upper electrode ofthe capacitor. The material of the doped semiconductor layer 260 may beN-doped semiconductor. The material of the conductor layer 270 may bemolybdenum, chromium, iridium, aluminum, titanium, combination thereofor alloy thereof.

Embodiment II

Reference is made to FIGS. 3A˜3D, which are cross-sectional viewsshowing a method for manufacturing a control element of an organicelectro-luminescent display according to another preferred embodiment ofthe invention.

In FIG. 3A, a first gate electrode 322, a bottom electrode 324 of acapacitor and a second gate electrode 326 are formed on an insulatingsubstrate 310. The material of the first gate electrode 322, the bottomelectrode 324 of the capacitor and the second gate electrode 326 may bemolybdenum, chromium, iridium, aluminum, titanium, combination thereofor alloy thereof. The forming method may be physical vapor depositionfirst, which deposits a conductor layer, such as sputtering and thenpatterning the conductor layer by, for example, photolithography.

In FIG. 3B, a first gate dielectric 332 and a first channel 342 areformed over at least part of the first gate electrode 322; a stackdielectric 334 of the capacitor is formed on the bottom electrode 324 ofthe capacitor; and a second gate dielectric 336 and a second channel 346are formed over at least part of the second gate electrode 326. Thematerial of the first gate dielectric 332, the stack dielectric 334 andthe second gate dielectric 336 may be silicon oxide, silicon nitride orcombination thereof. The material of the first channel 342 and thesecond channel 346 may be amorphous silicon. The forming method may bedone by following steps. A dielectric layer is deposited first. Then,the dielectric layer is patterned to form the first gate dielectric 332,the stack dielectric 334 and the second gate dielectric 336, such as byphotolithography. After the dielectric layer is patterned, asemiconductor layer is deposited. Then, the semiconductor layer ispatterned to form the first channel 342 and the second channel 346, suchas by photolithography. Follow-up steps are the same as the stepsillustrated in the Embodiment I.

Embodiment III

Reference is made to FIGS. 4A˜4D, which are cross-sectional viewsshowing a method for manufacturing a control element of an organicelectro-luminescent display according to still another preferredembodiment of the invention.

In FIG. 4A, a first gate electrode 422, a bottom electrode 424 of acapacitor and a second gate electrode 426 are formed on an insulatingsubstrate 410. The material of the first gate electrode 422, the bottomelectrode 424 of the capacitor and the second gate electrode 426 may bemolybdenum, chromium, iridium, aluminum, titanium, combination thereofor alloy thereof. The forming method may be physical vapor depositionfirst, which deposits a conductor layer, such as sputtering and thenpatterning the conductor layer by, for example, photolithography.

In FIG. 4B, a first gate dielectric 432 and a first channel 442 areformed over at least part of the first gate electrode 422; a stackdielectric 434 and a stack semiconductor layer 444 of the capacitor areformed on the bottom electrode 424 of the capacitor; and a second gatedielectric 436 and a second channel 446 are formed over at least part ofthe second gate electrode 426. The material of the first gate dielectric432, the stack dielectric 434 and the second gate dielectric 436 may besilicon oxide, silicon nitride or combination thereof. The material ofthe first channel 442, the stack semiconductor layer 444 and the secondchannel 446 may be amorphous silicon. The forming method may bedepositing a dielectric layer and a semiconductor layer first and thenpatterning the dielectric layer and the semiconductor layer, such as byphotolithography. Follow-up steps are the same as the steps illustratedin the embodiment I.

In conclusion, the embodiments of the invention have the advantages of:

(1) reducing the use of photolithography because the etching stop layerand the hole are formed in the same step;

(2) possibly not needing to change the electrical characteristics whenthe capacitance of the capacitor is changed; and

(3) possibly not needing to change the geometric characteristics whenthe capacitance of the capacitor is changed.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the structure of the presentinvention without departing from the scope or spirit of the invention.In view of the foregoing, it is intended that the present inventioncover modifications and variations of this invention provided they fallwithin the scope of the following claims and their equivalents.

1. A control element for an organic electro-luminescent display, thecontrol element comprising: a first transistor having a first gateelectrode electrically connected to a scan line, a first source/drainelectrode electrically connected to a data line and a secondsource/drain electrode; a second transistor having a second gateelectrode electrically connected to the second source/drain electrode, athird source/drain electrode electrically connected to a working voltageand a fourth source/drain electrode electrically connected to a lightemitting diode; the first and second transistors also having gatedielectrics; a capacitor having a bottom electrode electricallyconnected to a reference voltage and an upper electrode electricallyconnected to the second gate electrode; and an etching stop layer formedon sidewalls of the gate dielectrics; and the etching stop layer alsoformed on both a channel of the first transistor and a channel of thesecond transistor and filling a first gap between the bottom electrodeof the capacitor and the first gate electrode of the first transistor,wherein a material of the etching stop layer is the same as a materialof a dielectric layer of the capacitor.
 2. The control element of claim1, wherein the etching stop layer further fills a second gap between thebottom electrode of the capacitor and the second gate electrode of thesecond transistor.
 3. The control element of claim 1, wherein theetching stop layer covers at least a part of the second gate electrodebut has a hole therein, and the upper electrode of the capacitor has aconnecting part electrically connected to the second gate electrodethrough the hole of the etching stop layer.
 4. The control element ofclaim 3, wherein the connecting part comprises: a conductor layer; and adoped semiconductor layer separating the conductor layer and the secondgate electrode.
 5. The control element of claim 1, wherein the capacitorhas a capacitor stack positioned between the bottom electrode and thedielectric layer of the capacitor.
 6. The control element of claim 5,wherein the capacitor stack has a stack dielectric positioned over thebottom electrode of the capacitor.
 7. The control element of claim 6,wherein a material of the stack dielectric is the same as a material ofthe gate dielectric of the first transistor.
 8. The control element ofclaim 6, wherein a thickness of the stack dielectric is the same as athickness of the gate dielectric of the first transistor.
 9. The controlelement of claim 6, wherein the capacitor stack has a stacksemiconductor layer positioned over the stack dielectric.
 10. Thecontrol element of claim 9, wherein a material of the stacksemiconductor layer is the same as a material of the channel of thefirst transistor.
 11. The control element of claim 9, wherein athickness of the stack semiconductor layer is the same as a thickness ofthe channel of the first transistor.
 12. The control element of claim 1,wherein the material of the dielectric layer of the capacitor isdifferent from a material of the gate dielectric of one of the firsttransistor and the second transistor.
 13. The control element of claim1, wherein a thickness of the dielectric layer of the capacitor isdifferent from a thickness of the gate dielectric of one of the firsttransistor and the second transistor.